1. Field of the Invention
This invention relates to a seat slide unit in a vehicle, etc., and more particularly to a seat slide unit comprising an operation bar extending from side to side on the lower side of a seat for operating lock mechanisms between lower and upper rails.
The present application is based on Japanese Patent Applications No. Hei. 10-66707, 10-66708 and 10-77158, which are incorporated herein by reference.
2. Description of the Related Art
As a seat slide unit, the following type one is known.
An operation bar in such a seat slide unit, which is substantially U-shaped, is also known as a towel bar while the seat slide unit is also known as a towel bar type slide unit. Left and right lock mechanisms are locked and unlocked by manipulating the operation bar. The left and right lock mechanisms comprise left and right upper rails on the seat bottom side that can be locked and unlocked with respect to left and right lower rails on the floor side. The left lock mechanism is placed between the left lower rail and the left upper rail and the right lock mechanism is placed between the right lower rail and the right upper rail. The operation bar is rotatably supported at both end parts in front portions of the left and right upper rails for rotation and is extended in the intermediate portion substantially in a horizontal direction from side to side. The operation bar is coupled at both end parts to the left and right lock mechanisms. It is rotated upward, whereby the left and right lock mechanisms are unlocked synchronously so as to enable slide adjustment of the seat back and forth. The operation bar is restored downward, whereby the left and right lock mechanisms are locked synchronously so as to lock the seat at the slide adjustment position.
If the seat slide unit comprises a rod that can be rotated on the back-and-forth axis at a constant position of the upper rail, for example, and the lock mechanism is locked or unlocked in response to the rotation direction of the rod, the rod and the end part of the operation bar are coupled by a link. That is, the link is attached at a base end part to the rod and engages at a tip part the operation bar, whereby the lock mechanism is operated in response to the rotation direction of the operation bar. In this structure, the tip part of the link rotated on the back-and-forth axis engages the end part of the operation bar rotated on the side-to-side axis, thus the engagement position of the tip part of the link and the end part of the operation bar shifts in the length direction of the link in response to the rotation position of the operation bar.
By the way, the operation bar in the seat slide unit has comparatively high rigidity, for example, as a steel pipe about 12 mm in diameter bent substantially like 1.1 considering the strength and operability of the operation bar.
However, since the conventional seat slide unit comprises the left and right lock mechanisms coupled directly to both end parts of the operation bar of comparatively high rigidity, for example, if the positional relationship between the left and right upper rails shifts because of an attachment accuracy error of the unit itself, dimension errors of the components, deformation of the components at the operation time, etc., it is feared that a large deformation load may be imposed on the coupling parts of the operation bar and the left and right lock mechanisms and interfere with smooth operation of the left and right lock mechanisms, making it impossible to cause the left and right lock mechanisms to lock and unlock reliably in synchronization with each other.
Further, since the operation bar of comparatively high rigidity is rotatably supported at both ends at constant points of the left and upper rails, it is feared that a large deformation load may be imposed on the rotatably-supporting parts at both ends of the operation bar and interfere with smooth operation of the lock mechanisms, for example, because of an attachment accuracy error of the unit itself, dimension errors of the components, deformation of the components at the operation time, etc., making it impossible to cause the lock mechanisms to lock and unlock reliably. On the other hand, if attachment accuracy of the unit itself and dimension accuracy of the components are enhanced, a new problem of incurring an increase in costs of the whole unit accordingly arises.
Still further, in the conventional seat slide unit comprising such a link, the steel link engages the steel operation bar directly. However, since the conventional seat slide unit comprises the steel link engaging the steel operation bar directly, it is feared that a rattle or noise may occur in the engagement part of the link and the operation bar. To prevent a rattle or noise from occurring, it becomes necessary to urge the operation bar by a spring so as to elastically strongly press the engagement part of the link and the operation bar or guide a shift in the engagement part of the link and the operation bar with high accuracy, resulting in complication of the structure of the whole unit and high costs.